Earth's only natural satellite has different phases due to its revolution around the planet. This causes the light from the sun to strike the moon at different angles, and this sunlit appearance is the one perceived by any observer on Earth.
The time it takes for the moon to complete one lunar cycle is 29.5 days. As the moon orbits Earth during this period, its alignment with the sun varies. For example, when the moon is in its new phase, its position is directly between Earth and the sun. During this phase, the moon is not visible from Earth. The opposite occurs during a full moon when the moon's illuminated side is fully visible during nighttime on Earth.